It started out as a friendship, as many relationships do. But gradually Sam's feelings for Kat, a beautiful, smart and confident woman, had turned romantic.

Hang on — there’s a catch. Sam and Kat met in the virtual world Second Life. And although they shared all kinds of intimacies in Second Life, the real people have never laid eyes on each other.

That didn’t seem to matter to Sam. He fell pretty hard for his avatar sweetie. They bonded intellectually, emotionally, and yes, thanks to Second Life animations, even physically.

Here’s where it gets complicated. Unlike his avatar, which is female, in real life, Sam is a man. A married man. And the person behind the blonde, curvaceous Kat? Married. And, quite possibly, a man, too.

(As you might imagine, some people interviewed for this story did not want to reveal their full names. Some gave us their avatar names, while others went with pseudonyms.)

Sam knew from the outset that he had no intention of ever meeting Kat in real life. So although he acknowledges feeing some guilt, he didn’t see the online affair as being as damaging as a real one.

“With Second Life, there wasn't the fear of a real-life physical attachment,” he says. “The fear of someone calling me up at home.”

For many folks, the arms-length quality of in-game romance is what separates a (fairly) harmless experiment from actual infidelity. If these intimacies, no matter how personal, never translate into a real-world meeting or real-life sex, can it be considered cheating?

The majority of people who responded to the MSNBC.com/iVillage Lust, Love and Loyalty survey think it can — although that characterization tends to skew along gender lines.

Sending a sexually flirtatious e-mail to a co-worker? Just over half of men — 53 percent — think that’s cheating, as compared with 73 percent of women. Ratchet that up to online talk or “Webcamming,” and the cheating meter ticks up slightly: 57 percent of men think that’s a no-no, while 77 percent of women do.

Even Sam wasn’t sure how to term his relationship. After all, he was role-playing.

“It’s a 3-D avatar having sex with another 3-D avatar,” says Wagner James Au, author of the Second Life blog New World Notes. “What looks like a hot blonde babe could be a 60 year-old man in Milwaukee.”

But at some point, Sam’s in-world relationship with Kat began to intrude on his real life. A recent family vacation was punctuated by furtive Second Life meetings with his avatar girlfriend.

“I dreamed up any excuse I could with my family to tell them I needed to get online for a few minutes here and there,” he says. “It was pathetic.”

That’s where the lines get blurry, says P. Shavaun Scott, a marriage and family therapist from San Luis Obispo, Calif.

“If people are getting their needs for love, attention, intimacy, companionship and sex from somewhere else, I think it’s cheating,” she says. “And, if they’re keeping their relationship a secret from their real-life partner.”

When Kat’s real-life spouse began getting suspicious, things between the Second Life couple began to deteriorate. Sam says Kat became paranoid. She started having outbursts.

“She no longer became the funny, excited and refreshing girl I had fallen for,” he says.

There was a breakup, a half-hearted reconciliation and a final breakup. What Sam didn’t expect, he says, is how much the virtual breakup would affect him.

“My feelings for Kat were no different in many ways than what happens in a real-life relationship,” he says. “All the way down to a breakup.”

“It’s not the sex, it’s the emotional intimacy,” says Au. “You’re online at 2 a.m. getting very personal and talking about stuff that you should only be talking about with your boyfriend, girlfriend or whatever.

Some folks use virtual relationships as a way to experiment. The excitement is what initially drew Sam to hook up with Kat. And plenty of people are interested in the sex aspect of the hookups. “It’s a more interactive form of masturbation,” says Au. “And everyone’s going to do that on occasion.”

Amanda, 20, started up a friendship with someone she met in “World of Warcraft.” Her real-life relationship was one that she terms as “moderately abusive,” and her real-life boyfriend as “very controlling.” Her in-game guy, Joel, was much nicer. He spent hours teaching her how to play the game. They went on raids together. In-game chat graduated to AIM chat. Then long telephone conversations.

“You talk about your day, your dreams, that kind of thing.” she says. “I couldn’t get that from my real-life boyfriend.”

Max, 39, isn’t sure what drove his soon-to-be-ex-wife to have a relationship in Second Life. He says she refused to talk about it, and if he asked questions, she’d just hop online and freeze him out.

“I thought she was going through a depression and she’d get bored and move on with life,” he says. “But she kept getting deeper and deeper.”

Within six months of signing up for Second Life, Max’s wife was spending up to eight hours a day online — and even more on the weekends. She and her in-world boyfriend were in constant contact — even when they weren’t in-world. Max says he found out later that his wife and her avatar boyfriend were having drinks together — in his house — via Web cam.

Max went on Google and started doing some detective work. To his amazement, he learned that his wife had married her in-world boyfriend in Second Life.

“I had my dad looking over my shoulder at the stuff I was finding,” he says. “Just so I could ask him ‘Am I crazy? Am I really seeing this?’”

Max ended up pulling the Internet connection out of the wall, and he says his wife started trashing the house. The end came, says Max, when she threw a punch.

“I’m 6 foot, 200 pounds,” he says. “When she took a swing, I said, ‘no, we’re not going past this point.’” The two are currently finalizing divorce proceedings.

Although Max’s wife did end up meeting her virtual boyfriend in the real world, that often isn’t the case with virtual relationships. Sarah had a plane ticket bought and plans to meet her virtual partner, Martin — but she canceled her trip.

“One day I had the realization that I didn’t really want that guy,” she says. “What I wanted was for my husband to treat me like that guy.”

Sarah and her husband split up, and have since divorced. But Sarah credits Second Life with showing her what she wanted from a partner — attention, affection and romance. She gets all that from her current real-life boyfriend — a guy Sarah says she’ll probably marry.

And even though Sarah’s boyfriend didn’t ask her to, she ended her Second Life relationship last year. As a result, she doesn’t go in-world that much anymore.

“I decided that I didn’t want to partition my love,” she says. “I just wanted to have one person to call ‘sweetheart.’”